Could someone please check my work?

1. 1) when Typing a report, a certain Typist makes i errors with probability. pi (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 is? ( a ) 2 pi =.20 +. 35 +. 25 +.15 = . 95 Put... + M ( 6 ) pi =. 20 +. 35 +. 25 = 0.8