Answer:
(a)

(b)

(c)

(d)

Step-by-step explanation:
(a)

we can use property of exponent

we get


........Answer
(b)

we can use property of exponent

we get


........Answer
(c)

we can use property of exponent

we get



........Answer
(d)

we can use property of exponent

we get


we can use property

........Answer
it is 20 minuets that she went over on her bill