Affiliated Managers Group Inc. soared on news that it added another boutique money manager to its growing collection. The Prides Crossing firm also reported first-quarter economic net income that rose 11 percent to $137.9 million, or $2.48 per share, beating analyst estimates. Economic net income climbed to $137.9 million, compared to $124.2 million a year ago. AMG said it will acquire a majority stake in Veritas Asset Management LLP, a global equities manager with $17 billion in assets and 32 employees. Veritas is AMG’s fourth acquisition since December.