IF THEN syntax error

Hi Guys - I'm getting the Syntax error below on this IF formula:

IF(

${Leads.No. of Employees} > 2999,${Leads.No. of Employees}*(4.90/0.7)*12,

IF(

${Leads.No. of Employees} > 1499,${Leads.No. of Employees}*(5.90/0.7)*12,

${Leads.No. of Employees}*(6.90/0.7)*12

))

SYNTAX error message:

Syntax Error. Check the examples for any functions you're using to see if you formatted them correctly. Make sure your fields are formatted like this: ${Module Name.Field Name}.

Grateful for any tips on solving please.

Thank you, Ash