First, let's find 15% of 183,000.
[tex]0.15\cdot183,000=27,450[/tex]The down payment is $27,450.
(a) To find the amount of the loan, we just have to subtract.
[tex]183,000-27,450=155,550[/tex]Hence, the loan amount is $155,550.
(b) The monthly payment formula is
[tex]M=\frac{i\times P\times(1+i)^n}{(1+i)^n-1}[/tex]Where P = 155,550. i = 0.06/12. n = 360 (number of payments). Let's replace these values.
[tex]\begin{gathered} M=\frac{0.005\times155,550\times(1+0.005)^{360}}{(1+0.005)^{360}-1} \\ M=\frac{777.75(6.02)}{6.02-1}=\frac{4,682.06}{5.02}=932.68 \end{gathered}[/tex]Hence, the monthly payment is $932.68.
(c) We repeat the process but instead of using 6% interest, we are going to use 7% interest.
P = 155,550.
i = 0.07/12.
n = 360.
Then, we replace the values in the formula.
[tex]\begin{gathered} M=\frac{0.0058\times155,550\times(1+0.0058)^{360}}{(1+0.0058)^{360}-1} \\ M=\frac{902.19(8.02)}{8.02-1}=\frac{7,235.56}{7.02}=1,030.71 \end{gathered}[/tex]Hence, the monthly payment is $1,030.71 with 7% interest.