Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface. This solder was a tin-lead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What does hot air solder leveling ensure the coated copper will have?
Ah, so.. solderable surface

Donald Wills Douglas, Sr. built a plant in 1922 at Clover Field (Santa Monica Airport) for the Douglas Aircraft Company. In 1924, four Douglas-built planes took off from Clover Field to attempt the first aerial circumnavigation of the world. Two planes made it back, after having covered 27,553 miles (44,342 km) in 175 days, and were greeted on their return September 23, 1924, by a crowd of 200,000 (generously estimated). The Douglas Company (later McDonnell Douglas) kept facilities in the city until the 1960s.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What did Clover Field built airplanes attempt the first of?
Ah, so.. aerial circumnavigation of the world

Beside the introduction of the lute to Spain (Andalusia) by the Moors, another important point of transfer of the lute from Arabian to European culture was Sicily, where it was brought either by Byzantine or later by Muslim musicians. There were singer-lutenists at the court in Palermo following the Norman conquest of the island from the Muslims, and the lute is depicted extensively in the ceiling paintings in the Palermo’s royal Cappella Palatina, dedicated by the Norman King Roger II of Sicily in 1140. His Hohenstaufen grandson Frederick II, Holy Roman Emperor (1194 - 1250) continued integrating Muslims into his court, including Moorish musicians. By the 14th century, lutes had disseminated throughout Italy and, probably because of the cultural influence of the Hohenstaufen kings and emperor, based in Palermo, the lute had also made significant inroads into the German-speaking lands.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What building has ceeiling painting dedicated to the lutenists? 
Ah, so..
Palermo’s royal Cappella Palatina,