Bank of America’s Merrill Lynch unit said it will offer robo-advisory to its customers. The bank announced plans for an online service and app called Merrill Edge Guided Investing, which like other robo advisers will query customers about their age, income, risk tolerance as well as their investment goals and time horizon. A basket of exchange-traded funds tailored to the answers would then be recommended. It will be billed as a low-cost way of investing modest sums. The bank will offer an online version to clients and then to everyone else nationally in the first quarter. Aron Levine, head of Merrill Edge, said the robo product will blend the capability of Merrill Edge’s online brokerage platform with Merrill experts’ wealth management knowledge.