The correct calculation for the variable overhead spending variance is:
Variable Overhead Spending Variance = (Actual Variable Overhead - Standard Variable Overhead)
Plugging in the given values, we get:
Variable Overhead Spending Variance = ($8.00 x 4,500) - ($7.50 x 4,500)
Variable Overhead Spending Variance = $36,000 - $33,750
Variable Overhead Spending Variance = $2,250
Therefore, the variable overhead spending variance for material A is $2,250.