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

In the 18 years under the presidency of Edward Malloy, C.S.C., (1987–2005), there was a rapid growth in the school's reputation, faculty, and resources. He increased the faculty by more than 500 professors; the academic quality of the student body has improved dramatically, with the average SAT score rising from 1240 to 1360; the number of minority students more than doubled; the endowment grew from $350 million to more than $3 billion; the annual operating budget rose from $177 million to more than $650 million; and annual research funding improved from $15 million to more than $70 million. Notre Dame's most recent[when?] capital campaign raised $1.1 billion, far exceeding its goal of $767 million, and is the largest in the history of Catholic higher education.

The amount of professors at Notre Dame increased by what amount under Malloy?
500