If P = \(\sqrt{\frac{rs^3}{t}}\), express r in terms of p, s and t.

• A.\(\frac{p^2t}{s^3}\)
• B.\(\frac{p^3t}{s^3}\)
• C.\(\frac{p^3t}{s^2}\)
• D.\(\frac{pt}{s^3}\)
• E.