July sales for Melodic Kortholt, Limited, average μ₁ = $9,000 with σ₁² = $1,230. August sales average μ₂ = $7,300 with σ₂² = $1,435. September sales average μ₃ = $8,400 with σ₃² = $1,520.
(a) Find the mean and standard deviation of total sales for the third quarter. (Round your standard deviation to 4 decimal places.)