Calculate the value of a 4-year European call option on bond that will mature 5 years from today using Black's model. The 5-year cash bond price is $$\$ 105$$, the cash price of a 4-year bond with the same coupon is $$\$ 102$$ and both bonds have a principal of $$\$ 100$$. The strike price of the option is $$\$ 100$$, the 4-year risk-free interest rate is $10 \%$ per annum with continuous compounding, and the forward bond price volatility for the bond underlying the option is $2 \%$ per annum.