HINT: $$\sum_{k=1}^{34}\left(1.04^k\cdot1.05^{35-k}\right)=\sum_{k=1}^{34}\left(1.04^k\cdot1.05^{-k}\right)=1.05^{35}\sum_{k=1}^{34}\left(\frac{1.04}{1.05}\right)^k$$
Can you finish it from there?
HINT: $$\sum_{k=1}^{34}\left(1.04^k\cdot1.05^{35-k}\right)=\sum_{k=1}^{34}\left(1.04^k\cdot1.05^{-k}\right)=1.05^{35}\sum_{k=1}^{34}\left(\frac{1.04}{1.05}\right)^k$$
Can you finish it from there?