Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_56 (erp_w INTEGER, class VARCHAR, frequency_mhz VARCHAR)
### Question:
Name the sum of ERP W for class of d and frequency mhz of 98.7
### Answer:
SELECT SUM(erp_w) FROM table_name_56 WHERE class = "d" AND frequency_mhz = 98.7