If you want the effective yearly of the 10% convertible quartely just use the standard conversion formula however if you're looking for the effective yearly interest rate of the investment this is bow you go about it
We first have to work how long it takes for the accumulated value FV>100000
$$70000(1+T\times1.25\% )=100000\implies T=34.2857$$
Therefore T=35 is the smallest value such that FV>100000
$$FV=70000\left(1+35\times 1.25\%\right)\left(1+\frac{10\%}{4}\right)^{\frac{120-35}{3}}=202557.6949$$
$$70000(1+i)^{10}=202557.6949\implies i=11.21031493\%$$