MTBR (Main time between failure).

I'm trying to calculate the reliability of a hard disk. In the example of the book is not clear and when I try to calculate I get a different answer.

e=2.71828

time= 10 mins.

hours= 4000

formula: e-(1/MTBF) (T)

e-(1/4000)(10/60)

e(1/24,000) . (I can understand until here)

answer= 0.9999584. I don't get it how did they get this answer??? I tried many ways and I can't get this answer.

Someone explain me please