David\:is\:making\:rice\:for\:his\:guests,\:based\:on\:a\:recipe\:that\:requires\:rice,\:water\:and\:a\:special\:blend\:of\:spice.\:Where\:the\:rice\:to\:spice\:ratio\:is\:15\:to\:1.\:He\:currently\:has\:40\:grams\:of\:\:the\:spice\:blend\:and\:he\:can\:go\:buy\:more\:if\:necessary.\:He\:wants\:to\:make\:10\:servings\:where\:each\:serving\:has\:75\:grams\:of\:rice.\:Overall\:David\:spends\:4.50\:in\:rice.\:How\:many\:servings\:can\:David\:make\:with\:the\:current\:amount\:of\:spice\:he\:has?\: