Mary has $15 and she wants to buy some earrings. she picks one pair that costs $7.99 and two pairs that cost $2.59 each. which statement best describes if an exact total or an approximate total should be calculated?
a.
mary can round the prices of the earrings to the nearest dollar and then add to estimate if she has enough money.

b.
mary must add the exact cost of the three pair of earrings so she will know if she has enough money to buy the third pair.