Since the system is in equilibrium, the tension in the string is equal to the weight of the particle P. The weight of P is given by:

\(T = m_P imes g = 4 imes 10 = 40 \text{ N}\)

Thus, the tension in the string is 40 N.

For block B, the forces acting vertically are its weight, the tension in the string, and the normal reaction from the ground. Since B is in equilibrium, we have:

\(R + T = W_B\)

where \(R\) is the normal reaction, \(T\) is the tension, and \(W_B\) is the weight of block B.

The weight of block B is:

\(W_B = m_B imes g = 5 imes 10 = 50 \text{ N}\)

Substituting the known values:

\(R + 40 = 50\)

Solving for \(R\):

\(R = 50 - 40 = 10 \text{ N}\)

Therefore, the force exerted on B by the ground is 10 N.