The manager at Screaming Trees has been trying to calculate the portion of the​ company's overhead expenses that is fixed and the portion that is variable. Over the past twelve​ months, the number of yards of mulch processed was highest in​ July, when the total monthly overhead costs totaled $ 28 comma 000 for 37 comma 000 yards of mulch processed. The lowest number of yards of mulch processed in the last twelve months occurred in​ October, when total overhead costs were $ 22 comma 000 for 25 comma 000 yards of mulch processed. What was the variable cost per​ yard