java and data structures

Given the following recursive method, what would be the output assuming that the root is the passing value to node parameter private int unknown (Node node) { if (node == null) return 0; else return( 2*node.data + unknown(node.left)); } a. It will return the double of the summation of the data of the root node and only the data of the left nodes of the left subtree of the root node. b. It will return the summation of double of the data of the root with the data values of the subtree of the root node. c. It will return the double of the summation of the root node. O d. It will return the double of the summation of the left subtree of the root