GATE Civil Engineering (CE) 2015 Shift 1 Solved Paper

A 20 m thick clay layer is sandwiched between a silty sand layer and a gravelly sand layer. The layer experiences 30 mm settlement in 2 years.
Given:
${\mathit{T}}_{\mathit{v}}=\{\begin{array}{cc}\frac{\mathit{\pi }}{4}{\left(\frac{\mathit{U}}{100}\right)}^2& \mathrm{for}\mathrm{U}\le 60\%\\ 1.781-0.933{\log }_{10}\left(100-\mathit{U}\right)& \mathrm{for}\mathrm{U}>60\%\\ \end{array}.$
Where T_v is the time factor and U is the degree of consolidation in %.
If the coefficient of consolidation of the layer is 0.003 cm²/s, the deposit will experience a total of 50 mm settlement in the next _______________ years.