Simplify the following text for a Grade 9 native English-speaking person.
Original: Hurwicz hired Evelyn Jensen ( born October 31 , 1923 ) , who grew up on a Wisconsin farm and was , at the time , an undergraduate in economics at the University of Chicago , as his teaching assistant during the 1940s .
Simplified: Hurwicz hired Evelyn Jensen to help him teach during the 1940s . She grew up on a Wisconsin farm and was studying economics at the University of Chicago .