Could someone please check my work?

1. 1) when Typing a report, a certain Typist Makes errors with probabilitypi (izo), where Po=. 20 p, =. 35 P2=. 25 Pg =. 15 probability of no errors What is the probability That The Typist Makes ( a) at least 4 errors ( b ) at Most 2 errors ( a ) M 3 pi =. 20 +. 35 +. 25 +.15 0.5 = . 95 2 Put ... + M ( 6) ico - Pi = . 20 +. 35 +. 25 = 0.8