I need help with the Gold-192 and magnitude of the earthquake.​

Answer:a. about 18 hrsa. about 50 times largerStep-by-step explanation:"Gold-192 is a radioactive isotope with a half-life of 4.95 hours.  How long would it take for a 25 gram sample of Gold-192 to decay until only 2 grams remain?The amount A left after time t is:A = P (½)^(t / T)where P is the initial amount and T is the half life.Given A = 2, P = 25, and T = 4.95:2 = 25 (½)^(t / 4.95)0.08 = ½^(t / 4.95)log(0.08) = (t / 4.95) log(0.5)log(0.08) / log(0.5) = t / 4.95t = 4.95 log(0.08) / log(0.5)t ≈ 18"In May 2015, an earthquake originated in Galesburg, MI had a magnitude of 4.2 on the Richter scale.  In September 2012, a much smaller earthquake originating in Stony Point, MI had a magnitude of 2.5.  The magnitude of an earthquake is given by the formula m = log(I / I₀), where I is the intensity of the earthquake and I₀ is a small reference intensity, how many times larger was the intensity of the Galesburg earthquake compared to the Stony Point earthquake?"For the Galesburg earthquake:4.2 = log(I₁ / I₀)10^4.2 = I₁ / I₀I₁ = I₀ × 10^4.2For the Stony Point earthquake:2.5 = log(I₂ / I₀)10^2.5 = I₂ / I₀I₂ = I₀ × 10^2.5Divide the first equation by the second:I₁ / I₂ = 10^4.2 / 10^2.5I₁ / I₂ = 10^(4.2−2.5)I₁ / I₂ = 10^1.7I₁ / I₂ ≈ 50