Reflect the graph y = e^x over the line y = 3

Question

Could someone clarify the reflection of the function y = e^x over the line y = 3? I expected the reflection to be

y = -e^x +3 since y = -e^x is reflected over the line y = 0. However, the correct reflection is y = 6 - e^x. I am having trouble understanding why it is +6 and not +3

Answer 1

e^x has point (0,1), reflection over y=3 must have point (0,5). 3-1=5-3.

If -e^x passes through (0,5) then it approaches 6 as x is large negative

y=6-e^x passes through (0,5) and approaches 6 as x is large negative

could also just use y=-e^x+k,,,,,and use point (0,5),,,k=6