Weekly food expenditures for families of four in a large city average R420 with a standard deviation of R80. Assuming the weekly food expenditures are normally distributed. a) Find the interval of...

Weekly food expenditures for families of four in a large city average R420 with a standard deviation of R80. Assuming the weekly food expenditures are normally distributed.

a) Find the interval of weekly food expenditures that will include 99.7% of the families of four (rounded off to zero decimals).

b) What percentage of these weekly food expenditures are between R260 and R500 (rounded off to one decimal)?