An imaginary galaxy is considered to consist of `N` starts each of mass `M` and with each pair of stars at a mutual separation of `R`. If `N=4`, `R~~10^(21)m`, `M=2xx10^(30)kg`, find out the gravitational potential energy of galaxy.

Explanation

To find the gravitational potential energy of the imaginary galaxy consisting of \( N \) stars, we can follow these steps:

### Step-by-Step Solution

1. **Understanding the Gravitational Potential Energy Formula**:
The gravitational potential energy \( U \) between two masses \( m_1 \) and \( m_2 \) separated by a distance \( r \) is given by:
\[
U = -\frac{G m_1 m_2}{r}
...