Following up this question I would like to post the correct answer.

to solve this exercice, you have to use BA$2$ plus calculater. the solution should be as follow on the calculator:

CF $-2$nd $-$ clear work $-(-300000)-$ enter $-$ down $-25000-$ enter $-$ down $4-$ enter $-$ down $-40000$ enter $-$ down $-6$ enter $-$ IRR $-$ CPT $-$

you will get an answer of $2\mathrm{.}13$

$1\mathrm{.}0213=1\mathrm{.}045^$T then you calculate T which is the answer