25. which rule describes a transformation across the x-axis? (x, y) (-x, y) (x, y) (x, -y) (x, y) (y, x) (x, y) (-x, -y)

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?