Aturtle is at the bottom of a 20 foot well. each day it crawls up 4 feet but it slips back 2 feet. after how many days will the turtle reach the top of the well?

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?