the cost of a telephone call is 5 pesos for the first three minutes and an additional of 2 pesos for each additional minute or fractional part thereof. find the cost of all call lasting: a) .5 min, b) 3 minutes, and c) 5 minutes

c(t)=5+2(t-3), t>3 

a) c(0.5)=5
b) c(3)=5
c) c(5)=5+2(5-3)=5+2(2)=9