When investing in E-mail, diminishing returns apply after
a. $600,000 per segment.
b. $600,000 per product.
c. $800,000 per product.
d. $800,000 per segment.
e. $500,000 per product.
a. $600,000 per segment.
b. $600,000 per product.
c. $800,000 per product.
d. $800,000 per segment.
e. $500,000 per product.