If a2 + b2 + c2 = 16, x2 + y2 + z2 = 25 and ax + by + cz = 20, then the value of a + b + c isx + y + z

• A. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>3</center></td></tr><tr><td style="text-align: center;">5</td></tr></table>
• B. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>5</center></td></tr><tr><td style="text-align: center;">3</td></tr></table>
• C. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>4</center></td></tr><tr><td style="text-align: center;">5</td></tr></table>
• D. <table><tr><td rowspan="2"></td><td style="border-bottom:1px solid #000000;vertical-align:bottom;padding-bottom:2px;"><center>5</center></td></tr><tr><td style="text-align: center;">4</td></tr></table>