D.C.-based tech education juggernaut Blackboard Inc. is buying point-of-sale company Sequoia Retail Systems Inc. Sequoia provides hundreds of colleges with sales and inventory management systems, with a special footprint in the retail bookstore space. The terms of the deal, announced Tuesday, were not disclosed. The acquisition builds on Blackboard's own sales system, called Blackboard Transact, which enables students to use one college-issued card or their mobile devices to pay for everything...