The answer is C) $30.00.
First, find out how much 1lb costs. 1lb would cost 1/4 of 4lb.
$10×1/4=$2.50/1lb.
So 12 pounds would be 12x the cost of 1lb.
$2.50×12 pounds=$30/12lb.
Find out how many children there are first. Come on, this is simple fractions/percents/decimals/ratios.