Starting from rest a particle moves in a straight line with acceleration \[a={{(25-{{t}^{2}})}^{1/2}}m/{{s}^{2}}\] for \[0\le t\le \text{ }5s\], \[a=\frac{3\pi }{8}m/{{s}^{2}}\] for \[t>5s\]. The velocity of particle at \[t=7s\] is:

• A. 11 m/s
• B. 22 m/s
• C. 33 m/s  
• D. 44 m/s