$.$ State one advantage of the Miller$-$Orr Model over the Baumol Model.

b$.$ A company generates GHS$400,000$ per month excess cash, which it intends to invest in short term securities$.$ The interest rate it can expect to earn on investment is $20\%$ per annum. The transaction cost associated with each separate investment of funds is GHS$400.$

i$.$ Calculate the cost of making transactions per annum.

ii$.$ Determine the opportunity cost of holding cash per annum.

iii. Calculate the optimum amount of cash to be invested in each transaction