Test each of the following series for convergence by the Integral Test. If the Integral Test can be applied to the series, enter CONV if it converges or DIV if it diverges. If the integral test cannot be applied to the series, enter NA. (Note: this means that even if you know a given series converges by some other test, but the Integral Test cannot be applied to it, then you must enter NA rather than CONV.) [infinity]
a. ∑ ne^−7n
n=1
[infinity]
b. ∑n+6/(−9)
n=1

[infinity]
c. ∑ne^7n
n=1