Read this and answer the question. If the question is unanswerable, say "unanswerable".

The works of Virgil almost from the moment of their publication revolutionized Latin poetry. The Eclogues, Georgics, and above all the Aeneid became standard texts in school curricula with which all educated Romans were familiar. Poets following Virgil often refer intertextually to his works to generate meaning in their own poetry. The Augustan poet Ovid parodies the opening lines of the Aeneid in Amores 1.1.1–2, and his summary of the Aeneas story in Book 14 of the Metamorphoses, the so-called "mini-Aeneid", has been viewed as a particularly important example of post-Virgilian response to the epic genre. Lucan's epic, the Bellum Civile has been considered an anti-Virgilian epic, disposing with the divine mechanism, treating historical events, and diverging drastically from Virgilian epic practice. The Flavian poet Statius in his 12-book epic Thebaid engages closely with the poetry of Virgil; in his epilogue he advises his poem not to "rival the divine Aeneid, but follow afar and ever venerate its footsteps." In Silius Italicus, Virgil finds one of his most ardent admirers. With almost every line of his epic Punica Silius references Virgil. Indeed, Silius is known to have bought Virgil's tomb and worshipped the poet. Partially as a result of his so-called "Messianic" Fourth Eclogue—widely interpreted later to have predicted the birth of Jesus Christ—Virgil was in later antiquity imputed to have the magical abilities of a seer; the Sortes Vergilianae, the process of using Virgil's poetry as a tool of divination, is found in the time of Hadrian, and continued into the Middle Ages. In a similar vein Macrobius in the Saturnalia credits the work of Virgil as the embodiment of human knowledge and experience, mirroring the Greek conception of Homer. Virgil also found commentators in antiquity. Servius, a commentator of the 4th century AD, based his work on the commentary of Donatus. Servius' commentary provides us with a great deal of information about Virgil's life, sources, and references; however, many modern scholars find the variable quality of his work and the often simplistic interpretations frustrating.

When was the 12 book epic Thebaid written?
unanswerable