`.^(90)Sr` decays to `.^(90)Y` by `beta` decay with a half-life of `28` years. `.^(90)Y` decays by `beta`-to `.^(90)Zr` with a half-life of `64h`. A pure sample of `.^(90)Sr` is allowed to decay. What is the valued of `(N_(Sr))/(N_(y))` after (a) `1h` (b) `10` years ?

Explanation

To solve the problem, we need to find the ratio of the number of nuclei of Strontium-90 (Sr) to Yttrium-90 (Y) after specific time intervals. We'll use the decay equations and the half-lives provided.

### Given Data:
- Half-life of \( ^{90}Sr \) (Strontium-90) = 28 years
- Half-life of \( ^{90}Y \) (Yttrium-90) = 64 hours

### Step 1: Calculate Decay Constants
The decay constant \( \lambda \) can be calculated using the formula:
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