A company takes out a four-year, $800,000 mortgage on May 1. The interest rate on the loan is 5% per year, and blended payments of $18,423 (including both interest and principal) are to be made at the end of each month. The following is an extract from the loan amortization table the bank provided the company:

		Beginning Loan Balance		Payment		Interest		Principal		Ending Loan Balance
Payment 1		$800,000		$18,423		$3,333		$15,090		$784,910
Payment 2		784,910		18,423		3,270		15,153		769,757
Payment 3		769,757		18,423		3,207		15,216		754,541
Payment 4		754,541		18,423		3,143		15,280		739,261

Q: (a) The monthly payments will be the same amount each month, throughout the entire term of the loan. From the loan amortization table, we can see that the portion of the payment related to interest is decreasing each payment. Prepare a brief explanation for why this is happening.