Please solve - capital market analysis question

Firstly calculate risk neutral probability of making up move and down move. It is calculated as under:

(exp(r)-d)/(u-d) here r is risk free rate applicable for period under consideration, d is down price/initial price and u is up price/initial price. You need to use exponential function on any scientific calculator. Else it will be given in question paper. 

in this case risk neutral up probability is 75.64%. so the same for down probability is 24.36%.

Here if price moves up value of put is zero but if it moves down it is Rs. 5. probability of down move is 24.36% so expected value is 1.218. we further discount this using risk free rate to arrive at the value of Rs. 1.16

u=55/50= 1.1,  

d=45/50=0.90, 

r for 6 months = 6/12 =  0.05

C1=0

C2=50-45=5

value of put = [u-1-r /u-d] [C2/1+r]      

                   = [1.1 - 1 - 0.05/1.1 - 0.9] [5/1+0.05]

                   = [0.05/0.20] [4.76]

                   =1.19  [Minor difference of .03 to be ignored]