Solve part a and part b please

The half$-$life for the radioactive decay of U$-238$ is $4\mathrm{.}5$ billion years and is independent of initial concentration.

Part A

How long will it take for $14\%$ of the $U-238$ atoms in a sample of $U-238$ to decay?

Express the time in years to two significant figures.

Time $=$

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Part B

If a sample of $U-238$ initially contained $2\mathrm{.}6{10}^{18}$ atoms and was formed $4\mathrm{.}8$ billion years ago, how many $U-238$ atoms does it contain today? Express the number of atoms to two significant figures.

$N=$