Mr. Abernathy purchased a selection of wrenches for his shop. The total cost was $78. He bought the same number of $1.50 and $2.50 wrenches, and half that many $4 wrenches. The number of $3 wrenches was one more than the number of $4 wrenches. How many of each did he purchase?
_ $1.50 wrenches
_$2.50 wrenches
_$4 wrenches
_$3 wrenches.