During first 10s my velocity was $30 \text{ m/s}$ Eastward.
(a) So my instantaneous speed at 6s will be $30 \text{ m/s}$ Eastward.
During next 8s after first phase of 10s my velocity was $55 \text{ m/s}$ Westward.
(b) So my instantaneous velocity at 14s will be $55 \text{ m/s}$ Westward as this instant lies in the second interval of 8s.