Given: coefficient of discharge = 0.6

We know that the discharge over a right angled notch is given by the formula:

Q = Cd x (2g)^0.5 x L x H^2.5

where Q = discharge,
Cd = coefficient of discharge,
g = acceleration due to gravity,
L = length of the notch,
H = head of water above the apex of the notch.

Substituting the given values, we get:

Q = 0.6 x (2g)^0.5 x L x H^2.5

Now, we need to simplify this equation to get the answer in the required form.

Dividing both sides by (2g)^0.5, we get:

Q/(2g)^0.5 = 0.6 x L x H^2.5

Multiplying both sides by (2/H^2.5), we get:

(2/H^2.5) x Q/(2g)^0.5 = 1.2 x (L/H^2.5)

Now, we know that L/H^2.5 is a constant for a given notch. This constant is denoted by C and is given by:

C = L/H^2.5

Substituting this value in the above equation, we get:

(2/H^2.5) x Q/(2g)^0.5 = 1.2 x C

Simplifying, we get:

Q = (1.2 x C x (2g)^0.5 x H^2.5)/2

Q = 0.6 x C x (2g)^0.5 x H^2.5

From the given options, we can see that the answer is in the form of H^2.5. Therefore, we need to express the constant C in terms of H.

From the geometry of the right angled notch, we know that:

C = (2/3) x b

where b is the breadth of the notch.

Now, we can express b in terms of H using the relation:

H = (2/3) x h

where h is the height of the notch.

Substituting this value in the expression for b, we get:

b = (2/3) x (H/(2/3))

b = H

Therefore, C = (2/3) x H

Substituting this value in the expression for Q, we get:

Q = 0.6 x [(2/3) x H] x (2g)^0.5 x H^2.5

Q = 0.4 x (2g)^0.5 x H^4.5

Q = 1.417 x H^5/2

Therefore, the correct answer is option B, i.e., 1.417 H^5/2.