Question:
Which employer did Mary Meeker work for in May, 1990?

Context:
 Mary Meeker works for Morgan Stanley from Jan, 1991 to Jan, 1991. 
 Mary Meeker works for Merrill Lynch from Jan, 1982 to Jan, 1986. 
 Mary Meeker works for Salomon Brothers from Jan, 1986 to Jan, 1990. 
 Mary Meeker works for Cowen Group from Jan, 1990 to Jan, 1991.

Answer:
Cowen Group