Seasonal Index Calculation for Q3

A financial analyst is examining a company's quarterly sales data over the past three years in order to identify any seasonal patterns. The sales figures for Q1, Q2, Q3, and Q4 are as follows:

Year 1: Q1: $200k, Q2: $300k, Q3: $350k, Q4: $400k

Year 2: Q1: $220k, Q2: $330k, Q3: $380k, Q4: $450k

Year 3: Q1: $240k, Q2: $360k, Q3: $410k, Q4: $500k

To understand the seasonality, the analyst decides to calculate the average sales for each quarter across the years and then determine the seasonal indices by comparing these averages to the overall average sales.

What seasonal index will the analyst calculate for Q3?