SSS, SAS, ASA, AAS, HL OR NOT CONGRUENT

(Don’t answer if you don’t know just for points thanks)

Aparticular telephone number is used to receive both voice calls and fax messages. suppose that 25% of the incoming calls involve fax messages, and consider a sample of 25 incoming calls. (a) what is the expected number of calls among the 25 that involve a fax message?