Let X1, X2, X3 be three independent normal random variables with expected values μ1, μ2, μ3 and variances σ1^2, σ2^2, σ3^2, respectively. If μ1 = 10, μ2 = 20, μ3 = 30 and σ1^2 = σ2^2 = σ3^2 = 12, find P(54 < X1 + X2 + X3 < 72) (round off to second decimal place).