The probability p(x > 4) is

Direction: for the probability of a Gaussian variable x is given by

P_x(x) =	1	e^{– (x – 4)²/18}
	3√2π

Q. (0) = 0·5, Q		4		= 0·09176
		3

and Q. (2) = 0·02275

We know that general Gaussion probability density function is given by

P_x(x) =	1	e^{– (x – μ_x)²/2σ²_x}
	√2πσ_x

On comparing with given equation

P_x(x) =	1	e^{– (x – μ_x)²/2σ²_x}
	√2πσ_x

μx = 4, σ_x = 3

P(x > 4) = Q		x – μ_x		= Q		4 – 4
		σ_x				3

= Q(0) = 0·5