**Given Information:**

- Amount after 2 years = $6,200
- Amount after 3 years = $7,400

**Finding Principal:**

To find the principal, we need to subtract the interest from the total amount. Let's consider the amount after 2 years.

Let P be the principal, and r be the rate of interest. The formula to calculate the amount after 2 years is:

Amount = Principal + Interest
$6,200 = P + (P * r * 2)

Simplifying the equation, we get:
6,200 = P + 2Pr

**Finding Rate of Interest:**

Now, let's consider the amount after 3 years.

Using the same formula, but with 3 years:
$7,400 = P + (P * r * 3)

Simplifying the equation, we get:
7,400 = P + 3Pr

**Solving the Equations:**

We now have a system of two equations with two unknowns. We can solve these equations simultaneously to find the values of P and r.

Equation 1: 6,200 = P + 2Pr
Equation 2: 7,400 = P + 3Pr

Multiplying Equation 1 by 3 and Equation 2 by 2 to eliminate P, we get:
18,600 = 3P + 6Pr
14,800 = 2P + 6Pr

Subtracting Equation 2 from Equation 1, we get:
3,800 = P

**Calculating Rate of Interest:**

Substituting the value of P back into Equation 1:
6,200 = 3,800 + 2(3,800)r
2,400 = 7,600r

Dividing both sides by 7,600, we get:
r = 0.3158

**Conclusion:**

The principal amount is $3,800 and the rate of interest is approximately 0.3158, or 31.58%.