Oscar Company has $55,000$ units of finished goods inventory on May $1.$ Projected sales volume for the next four months is: May, $200,000$ units; June, $180,000$ units; July, $210,000$ units; and August, $230,000$ units. If Oscar wants to maintain an ending finished goods inventory in each month equal to $20\%$ of the following month's sales volume, then the number of units in finished goods inventory on June $30($i$.$e$.,$ target ending inventory at June $30)$ should be:

$36,000$ units

$42,000$ units

$46,000$ units

$63,000$ units

Cannot be determined from the information provided