Answer:
2048
Step-by-step explanation:
The bulbs increase in a multiple of 2
Using the formula a(a^n) where a = 2 and n is the number of year
1 yr = 4
2yr = 8
3 yr = 16
4 yr = 32
5 yr = 64
6 yr = 128
7 yr = 256
8 yr = 512
9 yr = 1024
10 yr = 2048
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