To find the rate of depreciation, we can use the formula:
Rate of depreciation = (Total depreciation over the years) / (Total number of years)
Total depreciation over the years = $6000 + $5500 + $5000 = $16500
Total number of years = 3
Rate of depreciation = $16500 / 3 = $5500 per year
Therefore, in the sixth year, the amount of depreciation would be $5500.