An n$-$year bond with an annual coupon rate of r$\%$

has the following characteristics:

The face amount is $980.$

Coupons of $49$ are paid semiannually.

The annual nominal yield rate convertible semiannually is $($r$+1\mathrm{.}8)\%$

The purchase price is $915\mathrm{.}70.$

The redemption value is $1,000.$

Calculate n$.$

possible answer choices: $2,3,4,5$