Cheese Lover III

Jon loves cheese. He decides to make $100$ blocks of cheese. The distribution of the weight (in grams) of each block he makes follows IID Exp$\left(\dfrac{1}{250}\right)$ distribution. Let $W_i$ denote the weight of the $i$th block of cheese, and $T_{100}$ represent the total weight of the $100$ blocks of cheese. Using Central Limit Theorem, what is an approximation for $\mathbb{P}[T_{100} > 26000]$? The answer is in the form $\Phi(a)$ for some real $a$. $\Phi$ here is the CDF of the standard normal distribution. Find $a$.