The average amount spent by customers on a single visit to a particular supermarket is £42 with standard deviation £24. In addition, the amounts spent have a normal distribution.

Giving your answers to 2 decimal places, use Excel to find the following:

(a) What percentage of the supermarket's customers spend

in excess of £45 in a single visit?

(b) What percentage of the supermarket's customers spend

less than £25 in a single visit?

(c) What percentage of the supermarket's customers spend

between £35 and £55?

(d) The supermarket wishes to introduce a minimum amount

for which credit cards may be used which enables 85% of customers

to pay by credit cards. At what amount should this credit card

minimum be set?

I'm unsure how to answer this question any help would be really appreciated. Thanks