Pancho Gonzales, CA$,$ just bought some AA$-$rated U$.$S$.$ corporate bonds for clients' portfolios for $101\mathrm{.}50.$ The bonds pay an annual coupon rate of $9$ percent of par value semi annually and mature in ten years.

Gonzales is concerned, however, that he will only be able to reinvest the coupon payments at $6$ percent over the life of the bonds

If he is correct, what bond equivalent true return would his clients receive if they hold the bonds until maturity?

a $6\mathrm{.}36$ percent

b $7\mathrm{.}93$ percent

C$\mathrm{.}12\mathrm{.}52$ percent

d$.3\mathrm{.}97$ percent.

I attached the solution. I didn't understand how he got the numbers. Can you show me in details plz$.$