A manufacturer purchases 20,000 units of a product at $1 each, 15,000 at $1.15 each, and 5000 at $2 each. Using these units as weight and the total number of units as the sum of all weights, find the weighted average cost per unit.
1
$1.81 per unit
2
$1.28 per unit
3
$1.82 per unit
4
$1.18 per unit