Let's go through the problem step by step.

Given:

• Principal (P) = $400
• Annual interest rate (r) = 6% = 0.06
• Time (t) = 3 years
• Interest is simple interest.

Simple Interest Formula:

$I = P \times r \times t$ Where:

• $I$ is the interest earned,
• $P$ is the principal amount,
• $r$ is the annual interest rate (decimal),
• $t$ is the time the money is invested (in years).

(a) How much total interest will Lisa earn?

Substitute the values: $I = 400 \times 0.06 \times 3$

(b) What will the total amount in the account be (including interest)?

The total amount, $A$, is calculated as: $A = P + I$ Let me calculate these values for you.### (a) The total interest Lisa will earn is $72.

(b) The total amount in the account, including interest, will be $472.

Would you like further details or have any questions?

Here are 5 related questions to expand on this topic:

1. How would the total interest change if the interest rate was compounded annually?
2. What would happen if the interest rate was 8% instead of 6%?
3. How much interest would Lisa earn if she saved for 5 years instead of 3?
4. What formula would apply if Lisa made additional monthly deposits to the account?
5. How does compound interest differ from simple interest in long-term savings?

Tip: Simple interest is beneficial for short-term savings, but compound interest tends to generate more wealth over longer periods.