Here, $P = 20000,\ r = 0.04$ (must change percent to a decimal), and $t = 2$. Now, substitute into the formula to solve:

$I = 20000 \cdot 0.04 \cdot 2 = 1600.$

This means, at the end of two years, Ida will have to pay $1,600 in interest.

Here, $P = 10000,\ r = 0.07$, and $t = 1.5$.

Convert the months to years by dividing the number of months by 12.

$\mathrm{ 1.5\ years = \frac{18\ months}{12\ months} }$

Now, substitute into the formula to solve:

$A = \$ 10000(1 + \left( 0.07 \cdot 1.5 \right)) = \$ 11,050$

So, the total amount Lance must pay on an 18-month, $10,000 loan with a 7% simple interest rate, is $11,050.

The simple interest will be the total amount minus the principal:

$\$ 39980 - \$ 32875 = \$ 7105.$

The total simple interest on Julian's loan was $7,105.

Now, to find the interest rate on this loan if the term is three years, substitute the values into the simple interest formula and solve for $r$, the interest rate:

$P = 32875,\ t = 3$, and $I = 7105$:

$7105 = 32875 \cdot r \cdot 3$

$7105 = 98625 \cdot r$

$0.072 \approx r$

So, the interest rate on this loan was 0.072, or 7.2%.

First, calculate the simple interest for Loan 1:

$P = 15000,\ r = 0.06$, and $t = 3$.

Now, substitute into the formula to solve:

$I = 15000 \cdot 0.06 \cdot 3 = 2,700$

So, if you choose Loan 1, you will end up paying $2,700 in interest.

Next, calculate the simple interest for Loan 2:

$P = 15000,\ r = 0.045$, and $t = 5$.

Now, substitute into the formula to solve:

$I = 15000 \cdot 0.045 \cdot 5 = 3,375$

So, if you choose Loan 2, you will end up paying $3,375 in interest.

Since 2,700 < 3,375, you will pay less interest with Loan 1 than with Loan 2.