jetpack compose - How to use Card

MainActivity.kt

package com.cfsuman.jetpackcompose

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.compose.setContent
import androidx.compose.foundation.BorderStroke
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontStyle
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setContent {
            MainContent()
        }
    }


    @Composable
    fun MainContent(){
        Card(
            Modifier
                .fillMaxWidth(.95F)
                .padding(15.dp),
            backgroundColor = Color.Yellow,
            elevation = 8.dp,
            shape = MaterialTheme.shapes.medium,
            border = BorderStroke(3.dp, Color.Red),
        ) {
            Text(
                text = "I am a Card.",
                fontSize = 35.sp,
                fontStyle = FontStyle.Normal,
                fontWeight = FontWeight.Bold,
                fontFamily = FontFamily.SansSerif,
                modifier = Modifier
                    .padding(25.dp),
                textAlign = TextAlign.Center,
                color = Color.Blue
            )
        }
    }


    @Preview
    @Composable
    fun ComposablePreview(){
        //MainContent()
    }
}