{"trustable":false,"prependHtml":"\u003cscript\u003e window.katexOptions \u003d { disable: true }; \u003c/script\u003e\n\u003cscript type\u003d\"text/x-mathjax-config\"\u003e\n MathJax.Hub.Config({\n tex2jax: {\n inlineMath: [[\u0027$$$\u0027,\u0027$$$\u0027], [\u0027$\u0027,\u0027$\u0027]],\n displayMath: [[\u0027$$$$$$\u0027,\u0027$$$$$$\u0027], [\u0027$$\u0027,\u0027$$\u0027]]\n }\n });\n\u003c/script\u003e\n\u003cscript async src\u003d\"https://mathjax.codeforces.org/MathJax.js?config\u003dTeX-AMS-MML_HTMLorMML\" type\u003d\"text/javascript\"\u003e\u003c/script\u003e","sections":[{"title":"","value":{"format":"MD","content":"稍微一想就知道WNJXYK在上题计算安全系数的方法不靠谱,于是他被数学老师抓住了,然后将要被狠狠地责罚一顿。他准备买点礼物送给老师,让老师从轻发落。\n\n他准备买同一种礼物n件,有两种买法:\n1.单个买,每个价格为p\n2.m个一套一起买,每套价格为q\n\n为了省钱,WNJXYK想知道如何买最便宜。"}},{"title":"Input","value":{"format":"MD","content":"第一行一个正整数T,表示测试样例数量 (1≤T≤1e5)\n接下来每行四个正整数n,m,p,q (1≤n,m,p,q≤1e4)"}},{"title":"Output","value":{"format":"MD","content":"每个测试样例,输出一行,最小的花费"}},{"title":"Sample Input","value":{"format":"MD","content":"2\n1 2 2 1\n1 2 3 4"}},{"title":"Sample Output","value":{"format":"MD","content":"1\n3"}},{"title":"Hint","value":{"format":"MD","content":""}}]}