the answer for plan d should be 128,000

and for plan e should be 140,000

please answer comprehensively and clearly

-13.6 Hill's operations manager (see Problems 13.3 through 13.5) is also considering two mixed strategies for JanuaryAugust: Produce in overtime or subcontracting only when there is no inventory. - Plan D: Keep the current workforce stable at producing 1,600 units per month. Permit a maximum of 20% overtime at an additional cost of $50 per unit. A warehouse now constrains the maximum allowable inventory on hand to 400 units or less. - Plan E: Keep the current workforce, which is producing 1,600 units per month, and subcontract to meet the rest of the demand. Evaluate plans D and E and make a recommendation. Note: Do not produce in overtime if production or inventory are adequate