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50

Step-by-step explanation:

42/n³∑k²+12/n²∑k+30/n∑1

=42/n³[n(n+1)(2n+1)/6]+12/n²[n(n+1)/2]+30/n [n]

=7n(n+1)(2n+1)/n³+6n(n+1)/n²+30

=7(n+1)(2n+1)/n²+6(n+1)/n+30

=[7(2n²+3n+1)+6(n²+n)+30n²]/n²

=[14n²+21n+7+6n²+6n+30n²]/n²

=[50n²+27n+7]/n²

=[50+27/n+7/n²]

→50 as n→∞

because 1/n,1/n²→0 as n→∞

  B.  50

Step-by-step explanation:

As n gets large, the fraction disappears, so the limit is 50.

e.

step-by-step explanation:

because there are always 10 numbers in a phone number.